1. Field of the Invention
This invention generally relates to a knife gate valve and, more particularly, to a sealing arrangement for securely retaining a valve seat within the valve against removal therefrom, and for preventing the valve seat from becoming packed with debris.
2. Description of the Prior Art
Knife gate valves are well known. It is also known to retain the valve seat of such a valve by several different types of seat-retention arrangements. For example, the valve seat may be adhered in place within the body of the valve by the use of adhesives. Alternatively, the valve seat may be pressed into place. In another variant, the valve seat may be retained in place with the use of retaining wires. In another mounting technique, the valve seat may be molded integrally as part of an elastomeric liner mounted within the valve body.
Although the known seat-retention arrangements have been generally satisfactory in use, they have not proven to be altogether reliable in operation, primarily because the valve seats, particularly for large-sized valves, are prone to being dislodged from their mounting and are prone to being packed with debris. During flow of a pressurized medium, even a low-pressurized medium, through the valve, the seat can be pulled out of its mounting due, among other things, to a pressure differential existing between the upstream and downstream sides of the seat, thereby destroying the utility of the valve seat and the valve itself.